What does ISO measure in photography?

ISO measures the sensitivity of the camera sensor to light, which is crucial for achieving proper exposure in photographs. A higher ISO setting allows the camera to capture images in lower light conditions by increasing the sensor's sensitivity. This means that even in dimly lit environments, the camera can register enough light to produce a well-exposed image.

When you increase the ISO, the sensor collects more light information, which is particularly useful for situations where using a slower shutter speed or wider aperture may not be practical. However, it's important to note that higher ISO settings can introduce digital noise, which can affect image quality. Using the appropriate ISO setting is a key aspect of balancing exposure with clarity in photography.

Other options do not pertain to the concept of ISO. Aperture size relates to how much light enters the lens and affects depth of field, distance to the subject does not influence the sensitivity to light, and color temperature pertains to the warmth or coolness of the light in the scene rather than sensitivity.